<p>The invention relates to a rotary knife assembly including a rotary shaft (20), a flange (21), a rotary knife (22) of an annular shape and a resilient member (31). The flange (21) includes a radially-outwardly protruding flange portion (23) having opposite end faces (23a; 23b) and a reduced diameter portion (24) disposed adjacent to the flange portion (23). The rotary knife (22) has opposite faces (22a; 22b) and is fitted on the reduced-diameter portion (24) of the flange (21) with one of the opposite faces (22b) directed toward one of the opposite end faces (23a) of the flange portion (23). The resilient member (31) is mounted on the flange (21) for urging the rotary knife (22) toward the flange portion (23). There is also provided a shifting mechanism (34, 35, 36) mounted on the flange (21) for shifting the rotary knife (22) in a direction away from the flange portion (23) against the urging force of the resilient member (31).</p>
